Absorption detector

Figure 24. Theoretical Temperature and Integral Temperature Curves Obtained from the Heat of Absorption Detector...

An ultraviolet absorption detector was used In tandem with a differential refractometer detector to obtain chemical composition data (3, 5 6). 

Figure 5.8 Scheaatic optical diagram of a variable wavelength dual beam absorption detector. A, and a photodiode array detector with reverse optics, B.

Stewart, J. E., Spectral-bandwidth effects of variable-wavelength absorption detectors in liquid chromatography, ]. Chromatogr., 174, 283, 1979. 

Woodruff, S. D. and Yeung, E. S., Refractive index and absorption detector for liquid chromatography based on Fabry-Perot interferometry, Anal Chem., 54, 1174, 1982. 

Svensson, L. M. and Markides, K. E., Fiber optic-based UV-absorption detector cell for high-temperature open tubular column liquid chromatography,... 

Table 8.80 shows the present status of speciation methodology. For trace-metal speciation, atomic absorption detectors feature a relatively high absolute detection limit (10 pg level), as compared to the 0.1 to 1 pg sensitivity level for molecular ion MS techniques as well as for MIP-AES. The detection limit of LEI-ToFMS is in the attogram range. Speciation has been reviewed [550]. Various monographs deal with speciation analysis [542,551,552]. 

Infrared absorption detectors arc available for hple, although they have never become very popular. From what you know about ir spectrometry and what you have read so far about hple detectors, see if you can decide whether the following statements are true or false. 

Andreae [712] used four different detectors in his investigations the electron capture detector (for the methylarsines), the quartz cuvette atomic absorption detector (for arsenic and antimony species), the graphite furnace atomic... 

The electron-capture detector was originally found to be a sensitive detector for the methylarsines [716]. After improvements of the atomic absorption detectors had been made (especially concerning adsorptive losses and peak shapes of the methylarsines), it was found that this detector could be used to replace the electron-capture detector, which because of its lack of specificity and its sensitivity to contamination and changes in operating conditions was very inconvenient to work with. 

HPLC has been used, with an ultraviolet absorption detector set for 254 nm, for the determination of aromatic hydrocarbons and with a flow calorimeter for the detection of all hydrocarbons. Increased sensitivity and decreased interference can be achieved with the ultraviolet absorption detector by measuring absorption at two wavelengths and using the ratios of the absorption at those wavelengths [28]. 

While a UV absorption detector is fairly sensitive, it is not universally applicable. The mixture components being measured must absorb light in the UV region in order for a peak to appear on the recorder. Also, the mobile phase must not absorb an appreciable amount at the selected wavelength. 

The basic theory, principles, sensitivity, and application of fluorescence spectrometry (fluorometry) were discussed in Chapter 8. Like the UV absorption detector described above, the HPLC fluorescence detector is based on the design and application of its parent instrument, in this case the fluorometer. You should review Section 8.5 for more information about the fundamentals of the fluorescence technique. 

As with the UV absorption detector, the sample compartment consists of a special cell for measuring a flowing, rather than static, solution. The fluorescence detector thus individually measures the fluorescence intensities of the mixture components as they elute from the column (see Figure 13.10). The electronic signal generated at the phototube is recorded on the chromatogram. 

Infrared spectroscopy is often used for qualitative analysis, and its powerful selectivity means that it can be used as a detector. However, the absorption of the eluent molecules, particularly in reversed-phase separations, often interferes with the detection of analytes. The infrared absorption detector therefore requires mechanical assistance to eliminate the solvent or needs powerful computer assistance to eliminate the background signal. 

Figure 2.8 Detection of alkylmercury compounds using flameless atomic absorption detector. Conditions column, Corasil I, 50 cm x 2.1 mm i.d. eluent, n-hexane flow rate, 0.5 ml min-1 detection, flameless atomic absorption spectrometer. Peaks 1, benzene, 2, ethylmercury chloride, and 3, methylmer-cury chloride.

CE is based on the use of narrow-bore capillaries with internal diameters typically betwen 20 and 150 pm. Because most commercial instruments equipped with ultraviolet/visible (UV-Vis) absorption detectors use a segment of the same capillary as the detection cell, the path length in CE is much less compared to those in HPLC or spectrometry. Therefore, the most commonly used CE detectors... 

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